Edit: it seems it is divided and cases have gone both ways in regards to expectation of privacy in apartment buildings: https://illinoislawreview.org/print/vol-2018-no-3/fourth-ame...
> Because the state offered credible testimony — specifically believed by the trial court — that third parties had unfettered access to the basement of this four-unit building, the defendant did not have a subjective expectation of privacy
GP suggested this wouldn’t be allowed in the hallway of an access-controlled building and precedent suggests that’s accurate. The key is whether a random person could wander into the area without encountering something analogous to a locked door.
If the door to the apartment block wasn’t locked (i.e. Joe Public could wander in and right up to your door), however, then when in the hallway a person would have no more expectation of privacy than when in the street.
Edit: Parent comment edited such that this makes no sense now